© 2016 American Chemical Society.The reactivity of the Ti=Ti double bond in (μ,η5:η5-Pn†)2Ti2 (1; Pn† = 1,4-{SiiPr3}2C8H4) toward isocyanide and heteroallene substrates, and molecules featuring homonuclear bonds between main-group elements (E-E) has been explored. Reaction of 1 with methyl isocyanide or 1,3-N,N′-di-p-tolylcarbodiimide resulted in the formation of the 1:1 adducts (μ,η5:η5-Pn†)2Ti2(μ,η2-CNMe) (2) and (μ,η5:η5-Pn†)2Ti2(μ-C{N(4-C6H4CH3)}2) (3), respectively, which are thermally stable up to 100 °C in contrast to the analogous adducts formed with CO and CO2. Reaction of 1 with phenyl isocyanate afforded a paramagnetic complex, [(η8-Pn†)Ti]2(μ,κ2:κ2-O2CNPh) (4), in which the "double-sandwich" architecture of 1 has been broken and an unusual phenyl-carbonimidate ligand bridges two formally Ti(III) centers. Reaction of 1 with diphenyl dichalcogenides, Ph2E2 (E = S, Se, Te), led to the series of Ti-Ti single-bonded complexes (μ,η5:η5-Pn†)2[Ti(EPh)]2 (E = S (5), Se (6), Te (7)), which can be considered the result of a 2e- redox reaction or a 1,2-addition across the Ti=Ti bond. Treatment of 1 with azobenzene or phenyl azide afforded [(η8-Pn†)Ti]2(μ-NPh)2 (8), a bridging imido complex in which the pentalene ligands bind in an η8 fashion to each formally Ti(IV) center, as the result of a 4e- redox reaction driven by the oxidative cleavage of the Ti=Ti double bond. The new complexes 2-8 were extensively characterized by various techniques including multinuclear NMR spectroscopy and single-crystal X-ray diffraction, and the experimental work was complemented by density functional theory (DFT) studies.
